Oil base drilling fluid and method of preparing same



Patented Oct. 8, 1940 I 1 1 UNITED STATES PATENT OFFICE v on. tast mme FLIlID AND METHODOF v j O'PREPARING Thomas V.Moore,=,Houst'on, Tex, assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application December 24, 1936, f

v Serial No. 117,519 1 10 Claims. (01, 255-1) In many drilling operations carried on by the pared by suspending'these materials in oil, the' rotary method, it is desirable to use a drilling weighting material tends to settle from the susfluid th'at is substantially free 'from' water and pension, and for this reason, oil base drilling for this purpose oil base drilling fluids have been fluids prepared in this manner are not entirely 5 developed. Such fluids are particularly apsatisfactory. v 5 plicable to drilling operations when 'anfaqueous v This invention relates to an improved'metho'd drilling fluid might disintegrate'the 'rockb'eing "of preparing oil base drilling fluids, comprising penetrated; for example, as indrilling through the suspension ofspent contact clay or other heaving shale, when the infiltration of water into powdered material that hasa greater tendency to the porous strata might be detrimental. vThese be wetted by oil ratherv than'by water, in an oil, .10 fluids are of value in the completion of oil Wells and adding thereto strong sulfuric acid, sulfonic with low reservoir pressure, or when it is desired acid, or sulfonates in order to reduce the tendency to obtain cores out without danger of water conof the weighting material to settle from the oil. t'amination, as for examp1e,'in determining the I have found that sulfuric acid has a marked water content of oil producing sands. effect in reducing the tendency of such materials '15 These fluids normally consist of a mineral oil, to settle from the oil. From 1 to 6%, by volume, such as crude oil, mixed with solid materials in has been found satisfactory for this purpose. As order to control the density and viscosity of the an example of the eiiectiveness of this reagent, drilling fluid. The basis of the improved drilling ve may cite the following example:

' fluid is an oil, preferably crude oil or an oil such 200 cc. of crude oil was mixed with 100 grams b as petroleumoil distillateor residue, or coal tar of spent contact clay'toform a drilling fluid of distillate or residue, or equivalent non-aqueous 8.5 lbs/gallon. After one hour of settling in a material that can be obtained in sufficient 100 cc; graduate, the clay had completely settled quantities at low cost. Tar of low viscosity may from the upper 5 ccgof the oil, and after 24 hours,

25 be usedas the base fluid. Other 011 basesare had completely' settledfrom theupp'er cc. of 25 crude oil which has been topped, gas oil,. lubrioil; By treating the same composition with 4 cc. eating oil, kerosene, naphthenates or the like. of concentrated sulfuric acid, a similar test indi- The oil is compounded withapowdered mineral cated that after 24 hours, the clay had only substance that is wet by oil in preference to water. settled from the upper 5 cc. of the oil. The same 30 One of the most useful materials that can be composition, when treated with 8 cc. of concen- 30 mixed with the oil is spent contact clay'from oil trated sulfuric acid only settled from the upper 3 refineries, which is a "fullers earth or similar cc. of the chat the end of 24 hours. Similar material through which mineral oilhas been tests, run on a mixture of 200 cc. of the same filtered. During the filtration process, the clay crude oil with 250 grams of the contact clay gave 5 or earth particles absorb carbonaceous or tar a drilling mudof a density of 9.9 lbs/gallon that 3 .materials from the oil and acquire the property settled from the upper cc. of the oil at the end of being specifically wet by 'oil in preference to of 24 hours. The same composition, when treated water. The powdered'weighting material also with 9 cc. of concentrated sulfuric acid settled can be a carbonaceous coated weighting material only from the upper 5 cc. of the oil.

such as any substance in the form of a powder, Another mud that had been prepared for drill- 40 coated with a film of tar or tarry material. The ing purposes was composed of about 250 barrels substance may be barytes, finelydivided calcium of Gulf Coast crude oil, 4 /2 barrels of concencarbonate, oyster shell, silica, sand,'iron oxide, trated sulfuric acid, and approximately 60 tons clays, or the like. Any of these powders can be of spent contact clay. The mud so prepared had carbonized by soaking them in a suitable petroa density of about 9.9 lbs/gallon. The stability 45 leum oil, vegetable oil or the like and igniting of the mud prepared in this manner was superior them. Other mineral substances may be used, to that of a similar batch of mud prepared without such as metallic sulfides, such as iron pyrite, lead the sulfuric acid. This mud was used to core sulfide, copper sulfide, and sphalerite or chalcothe producing section of sand in a Gulf Coast cite, oxides of lead, such as red lead or other field, which comprised about feet of high 50 mineral materials that have the property ofbeing pressure gas sand, about feet of oil sand, and specifically wetto oil without the necessity of about 10 feet of water sand. All operations were being treated with a carbonaceous or tarry macarried on without difilculty, and with no apterial. parent deterioration of themud.

5 I have found that when a drilling fluid is pre- I have found that settling of the clay is pre- 55 acid to produce lubricants of superior grades and also in the production of highly refined oils used for medicinal purposes. The sulfuric acid treatment results in the formation of oil soluble and water soluble sulfonates. During this treatment, a certain portion of the sulfonated compounds, principally the sulfo acids, remain in solution in the oil on separation of the acid sludge, and can be extracted from the oil. The oil soluble sulfonates are of particular value in maintaining the powdered mineral substance that is wet by oil in preference to wate r,'such as spent refinery clay in suspension in the gil. The sulfonates may include the metal salts of sulfonic acids.

The so-called sulfated alcoholsare also suitable foruse in this connection and, for the purpose of describing this invention, are included in the definition of sulfonated material obtained as the reaction products of sulfuric acid and hydrocarbon material. vvSulfated alcoholsare obtained by reactingfsulf uric acid upon unsaturated aliphatic hydrocarbons and the higher molecular weight compounds produced particularly are a suitableaddition substance for use in the mud fluid composition herein described.

Treatment with sulfuric acid results in other benefits to the oil base drilling fluid. In one instance, an oil base drilling fluid thathad not been treated with sulfuric acid became contaminated with ordinary aqueous drilling fluid and formed an emulsion that was too thick to pump; Treatment with a small quantity of sulfuric acid resulted in thinning of the emulsion and producing a fluid composition which could be pumped. In addition, I have found that treatment with sulfuric acid tends to form a water-inoil emulsion rather than an oil-in-water emulsion when the material becomes contaminated with water, which is an advantageous property in an oil base drilling fluid.

I have found that the sulfuric acid, sulfonic acid, or sulfonates may be added either to the weighting materials prior to its additionto the oil, to the oil prior to the addition of the weighting material, or to the mixture of weighting material and oil. However, conditions in practice are such that it is generally preferable to addthe sulfuric acid, sulfonic acid, or sulfonates after the oil and weighting material have been mixed.

While I do not wish to limit myself in this invention to any theory of its operation, I suggest the following mechanism for the results that I have obtained. I believe that the sulfuric acid, sulfonic acid, or sulfonates react either with the tarry material on the surface of the solid particles to form sulfonates, or with the materials in the oil capable of forming sulfonates, and that the sulfonates or sulfonic acids so formed become adsorbed on the surface of the solid particles and givethe results observed. I have observed that the addition of sulfuric acid, sulfonic acid, or sulfonates in this manner in the concentrations that we prefer to use, that is approximately 1 to 6%, does not materially affect the viscosity of the suspension, and this has led me to believe that the sulfuric acid, sulfonic acid, or sulfonates responsible for the stabilization do not act primarily as dispersing agents.

This invention is not to be limited to any example given merely for purposes of illustration, nor to any theory of the reactions, nor to any description of any particular product disclosed herei in, but only to the following claims in which I wish to claim all novelty; v

I claim; I

1. The method of stabilizing an oil base drilling fluid containing oil-wet clay, which comprisesadding' sulfuric acid to themixture.

2. Themethod of preparing an oil base drilling fluid, comprising treating finely divided solid material, in such a manner as to render its surface specifically wet to oil, and suspending the material in an oil containing sulfuric acid.

3. The method of preparing an oil base drilling fluid, comprising adding to a mineral oil spent contact clay,'used in the refining of petroleum oil, and, adding a small amount of sulfuric acid to the 'mixture' whereby the clay is maintained in suspension.

4. Anoil base drilling fluid, whichcomprises an oil in which is suspended a powdered mineral substance that is wet by oil in preference to water, and containing sulfuric acid.

5. An oil base drilling fluid, which comprises an oil in which is suspendeda powdered mineral material that is wet by oil in preference to water, and containing reaction products of hydrocarbon materials and sulfuric acid. I

6. A drilling fluid, comprising a mineral oil containing a dispersion of spent contact clay impregnated with tarry material, and sulfuric acid.

7. An oil base drilling fluid, comprising a mineral oil containing spent contact clay used in refining of petroleum oil to which has beenadded a small amount of strong sulfuric acid.

8. An oilbase drilling fluid, comprising an oil containing a suspended carbonaceous coated weighting material together with approximately 1 to 6% of strong sulfuric acid.

9. An oil base drilling fluid, comprising an oil containing suspended powdered silica coated with carbonaceous material, and containing sulfuric acid.

' 10. An 011 base drilling fiuid'in which is suspended clay which contains carbonaceous filter residue plus sulfuric acid.

THOMAS V. MOORE. 

